Liquid crystal TV (LCD TV) and liquid crystal display (all referred as LCD display devices here below), having the advantages of lightweight, small volume, low radiation, low power consumption, have become mainstream products in the market. Moreover, consumers are expecting large-sized and high-resolution LCD display devices.
Compared with the conventional cathode ray tube TV (CRT TV), the LCD display device has inferior performance in terms of contrast and color saturation. However, these disadvantages can be compensated by a superior backlight source.
Currently, the backlight source of LCD display devices is mainly classified as cold cathode fluorescent lamp (CCFL) and light emitting diode (LED).
Despite the CCFL has many advantages such as emission of excellent white light, low cost, high efficiency, long lifespan, good stability, and convenient operation, the CCFL has its disadvantages. For example, the products using CCFL are not environmental friendly (because mercury is contained), the color saturation is not enough (can reach only 70%˜80% of color saturation), and for the large-sized screen using CCFL, the working voltage is too high and the tube is too long.
In comparison, the LED has the following advantages such as low power consumption, long lifespan, small volume, light weight, and being environmental friendly. The color saturation of the LED can reach almost 100%. Drive time for the CCFL is about 1 sec˜2 sec, but the drive time for the LED are about 50 ns.
The LED backlight source can be classified as white light LED and RGB LED. By using color-filterless technology, the three color light emitted by the RGB LED is mixed in time-domain to produce white light. The white light LED has lower cost, but the RGB LED has superior color characteristics. When the RGB LED is used as the backlight source of the LCD display device, the contrast can reach the ratio of 50000:1.
FIG. 1 shows a first generally known LED driving architecture. Backlight unit 100 includes several LED modules 110 and LED drivers 120. Each LED module 110 includes a red light LED array 111, a green light LED array 112, and a blue light LED array 113. The red light LED array 111 has several serially connected red light LEDs. The green light LED array 112 has several serially connected green light LEDs. The blue light LED array 113 has several serially connected blue light LEDs. The LED driver 120 includes a red LED drive circuit 121 for driving the red light LED of an LED module, a green LED drive circuit 122 for driving the green light LED of an LED module, and a blue LED drive circuit 123 for driving the blue light LED of an LED module.
According to the first generally known technology, if the performance of brightness/color is not good in a particular LED, then the brightness/color of the LED array would also be negatively affected, causing the LED arrays to have different performance in terms of brightness/color.
FIG. 2 shows a second generally known LED driving architecture. The LED driving architecture includes a switching mode power supply (SMPS) 21, a bridge board 22, light source 23, a sensor 24 and a microcontroller 25.
The SMPS 21 includes an AC-to-DC converter 211 for converting an external AC voltage to a DC voltage. The red light (R) LED DC-to-DC converter 212 is for converting a DC voltage converted by the AC-to-DC converter 211 into a DC voltage applicable for driving the red light LED. The green light (G) LED DC-to-DC converter 213 is for converting a DC voltage converted by the AC-to-DC converter 211 into a DC voltage applicable for driving the green light LED. The blue light (B) LED DC-to-DC converter 214 is for converting a DC voltage converted by the AC-to-DC converter 211 into a DC voltage applicable for driving the blue light LED.
The bridge board 22 electrically connects the DC-to-DC converters 212˜214 to the red light, green light and blue light LED fixed current controllers 233˜235.
The light source 23 includes a substrate 231, several LEDs 232, and several red light, green light and blue light LED fixed current controllers 233˜235. The substrate 231 has several areas 231a˜231d. On each area are red light, green light and blue light LED fixed current controllers 233˜235, a red light LED array, a green light LED array and a blue light LED array.
The red light, green light and blue light LED fixed current controllers 233˜235 are used for applying a fixed current to the LEDs 232.
The sensor 24 is for detecting light emitted by the light source 23. The microcontroller 25 controls the red light, green light and blue light LED fixed current controllers 233˜235 according to the detection result of the sensor 24.
The disadvantages of the second generally known technology are similar to that of first generally known technology. That is, if the performance of brightness/color is not good in a particular LED, then the brightness/color of the LED array would also be negatively affected, causing the LED arrays to have different performance in terms of brightness/color.
Therefore, it needs an architecture for controlling the LED light source, which individually controls the brightness and color of each LED and is applicable to the image display apparatus such as LCD TV and LCD display.
Besides, the LED can also be used in daily life purposes such as illumination and traffic signs. Thus, the invention also provides an LED driving architecture, which independently controls the brightness and color of each LED.